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Separation of the ortho and para NMR signals in solid deuterium via DQ filtering
Tekijät: Malmi P, Punkkinen M, Ylinen E, Shevtsov V
Kustantaja: ACADEMIC PRESS INC
Julkaisuvuosi: 2000
Lehti:: Journal of Magnetic Resonance
Tietokannassa oleva lehden nimi: JOURNAL OF MAGNETIC RESONANCE
Lehden akronyymi: J MAGN RESON
Vuosikerta: 145
Numero: 2
Aloitussivu: 326
Lopetussivu: 333
Sivujen määrä: 8
ISSN: 1090-7807
DOI: https://doi.org/10.1006/jmre.2000.2094
Tiivistelmä
Double quantum (DQ) filtering is shown to lead to an effective separation of the NMR signals from the para (I = 1) and ortho (I = 2) molecules in solid deuterium. The separation is achieved by the pulse sequence 90(phi)degrees-t(pr)-90(phi)degrees-t(ev)-90(x)degrees-t, where the phase-cycled first two pulses create the Do coherence. Two components are observed after the third pulse; the para signal shows the maximum at a short time t while the ortho signal reaches the maximum at a longer t. The observed signal can be expressed as 1/2 Sigma(I) [F-1(t(pr) - t) - F-1(t(pr) + t)], where F-1(t) is a proper fitting function for the free induction signal of the para and ortho molecules (with I = 1 or 2, respectively). Numerical fits to experimental data at 4.2 and 2 K show that this method can be used to determine the ratio F-1(0)/F-2(0) and thus, because the initial value F-1(0) is proportional to the respective magnetization before the pulse sequence, the ortho and para concentrations in solid deuterium. (C) 2000 Academic Press.
Double quantum (DQ) filtering is shown to lead to an effective separation of the NMR signals from the para (I = 1) and ortho (I = 2) molecules in solid deuterium. The separation is achieved by the pulse sequence 90(phi)degrees-t(pr)-90(phi)degrees-t(ev)-90(x)degrees-t, where the phase-cycled first two pulses create the Do coherence. Two components are observed after the third pulse; the para signal shows the maximum at a short time t while the ortho signal reaches the maximum at a longer t. The observed signal can be expressed as 1/2 Sigma(I) [F-1(t(pr) - t) - F-1(t(pr) + t)], where F-1(t) is a proper fitting function for the free induction signal of the para and ortho molecules (with I = 1 or 2, respectively). Numerical fits to experimental data at 4.2 and 2 K show that this method can be used to determine the ratio F-1(0)/F-2(0) and thus, because the initial value F-1(0) is proportional to the respective magnetization before the pulse sequence, the ortho and para concentrations in solid deuterium. (C) 2000 Academic Press.
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